Really the only downside to the Netduino Go is the current lack of networking as at end May 2012.
Chris has already said (elsewhere) that this is only weeks away, and when it ships I suspect the Go will be the go, as it were. It is to Gadgeteer as C# is to Java - more or less the same but done better with the benefit of hindsight. Looking around the forums I see other platforms with either uneven hardware compatibility or mediocre driver quality.
There's also a possibility of onboard RTC. Not a certainty, but you never know your luck in the big city.
Something Chris (and the Gadgeteer guys) don't take enough credit for is the computer-as-a-network approach Gadgeteer and Go both take. The network stack on a single CPU system like the NetduinoPlus can never perform like one that has dedicated CPU with its own buffer, and pushing the network stack onto its own board gets it out of your application code space. I suspect that the Go, running on a Cortex M3 with a supporting cast of Cortex M0s smoothly integrated by the crunchy goodness of baked in virtualisation, is going to feel like developing on a much larger machine.
Some things none of the prototyping boards do well are
- Hardware watchdog reboot for hung application code
- OTAU (over the air update)
You need both of those for release grade hardware, which I guess means rolling your own. Netduino Go and Gadgeteer expressly support the notion of roll your own modules.